NFPA 497 - "Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas". Defines a "Flammable Liquid" as one that has a flash point lower then 100 degF.
This means Diesel or #2 heating oils, with a flash point of 152 degF, is a "combustible liquid" and not a "flammable" one. And as such, CEC sections 18 & 20 clearly do not apply to a combustible liquid, only a flamable one.
Here is a link with some reading on the subject... While this is a link that is based on the NEC, the situation is the same.
http://www.mikeholt.com/codeforum/ultimatebb.php?ubb=get_topic;f=22;t=000043
